From e2d63d1b34e92bcdb05c1f03de149989602003b5 Mon Sep 17 00:00:00 2001
From: Rich Harris <richard.a.harris@gmail.com>
Date: Sun, 30 Jul 2017 00:09:35 -0400
Subject: [PATCH] add dev mode warning for double destroy

---
 src/generators/dom/index.ts                   |  2 +-
 .../dev-warning-destroy-twice/_config.js      | 21 +++++++++++++++++++
 .../dev-warning-destroy-twice/main.html       |  1 +
 3 files changed, 23 insertions(+), 1 deletion(-)
 create mode 100644 test/runtime/samples/dev-warning-destroy-twice/_config.js
 create mode 100644 test/runtime/samples/dev-warning-destroy-twice/main.html

diff --git a/src/generators/dom/index.ts b/src/generators/dom/index.ts
index 33ac0a33c4..8c3f287b8d 100644
--- a/src/generators/dom/index.ts
+++ b/src/generators/dom/index.ts
@@ -264,7 +264,7 @@ export default function dom(
 		};
 
 		${name}.prototype.teardown = ${name}.prototype.destroy = function destroy ( detach ) {
-			if ( this._destroyed ) return;
+			if ( this._destroyed ) return${options.dev && ` console.warn( 'Component was already destroyed' )`};
 			this.fire( 'destroy' );
 			${templateProperties.ondestroy && `@template.ondestroy.call( this );`}
 
diff --git a/test/runtime/samples/dev-warning-destroy-twice/_config.js b/test/runtime/samples/dev-warning-destroy-twice/_config.js
new file mode 100644
index 0000000000..94c07ed6a7
--- /dev/null
+++ b/test/runtime/samples/dev-warning-destroy-twice/_config.js
@@ -0,0 +1,21 @@
+export default {
+	dev: true,
+
+	test(assert, component) {
+		const warn = console.warn; // eslint-disable-line no-console
+
+		const warnings = [];
+		console.warn = warning => { // eslint-disable-line no-console
+			warnings.push(warning);
+		};
+
+		component.destroy();
+		component.destroy();
+
+		assert.deepEqual(warnings, [
+			`Component was already destroyed`
+		]);
+
+		console.warn = warn; // eslint-disable-line no-console
+	}
+};
\ No newline at end of file
diff --git a/test/runtime/samples/dev-warning-destroy-twice/main.html b/test/runtime/samples/dev-warning-destroy-twice/main.html
new file mode 100644
index 0000000000..78e7012b82
--- /dev/null
+++ b/test/runtime/samples/dev-warning-destroy-twice/main.html
@@ -0,0 +1 @@
+<div/>
\ No newline at end of file